Cement compositions may be used in a variety of subterranean operations. For example, in subterranean well construction, a pipe string (e.g., casing, liners, expandable tubulars, etc.) may be run into a wellbore and cemented in place. The process of cementing the pipe string in place is commonly referred to as “primary cementing.” In a typical primary cementing method, a cement composition may be pumped into an annulus between the walls of the wellbore and the exterior surface of the pipe string disposed therein. The cement composition may set in the annular space, thereby forming an annular sheath of hardened, substantially impermeable cement (i.e., a cement sheath) that may support and position the pipe string in the wellbore and may bond the exterior surface of the pipe string to the subterranean formation. Among other things, the cement sheath surrounding the pipe string functions to prevent the migration of fluids in the annulus, as well as protecting the pipe string from corrosion. Cement compositions also may be used in remedial cementing methods, for example, to seal cracks or holes in pipe strings or cement sheaths, to seal highly permeable formation zones or fractures, to place a cement plug, and the like.
A broad variety of cement compositions have been used in subterranean cementing operations. In some instances, set-delayed cement compositions have been used. Set-delayed cement compositions are characterized by remaining in a pumpable fluid state for an extended period of time (e.g., at least about 1 day to about 2 weeks or more). When desired for use, the set-delayed cement compositions should be capable of being activated whereby reasonable compressive strengths are developed. For example, a cement set activator may be added to a set-delayed cement composition whereby the composition sets into a hardened mass. Among other things, the set-delayed cement composition may be suitable for use in wellbore applications, for example, where it is desired to prepare the cement composition in advance. This may allow, for example, the cement composition to be stored prior to its use. In addition, this may allow, for example, the cement composition to be prepared at a convenient location and then transported to the job site. Accordingly, capital expenditures may be reduced due to a reduction in the need for on-site bulk storage and mixing equipment. This may be particularly useful for offshore cementing operations where space onboard the vessels may be limited.
In addition to cementing, drilling and fluid displacement are two other subterranean operations that utilize treatment fluids. Drilling requires the use of drilling fluid or as it is also known, drilling mud. Drilling fluids may be used to maintain hydrostatic pressure in the wellbore, prevent formation damage, suspend cuttings, and to transport cuttings to the surface. Drilling fluids may be water-based or oil-based. Typical water-based drilling fluids may be composed of solely water or a mixture of water and various types of clay. Oil based drilling fluids typically use a base fluid of a petroleum product.
Fluid displacement utilizes one or more fluids to displace another fluid from the wellbore. Typically this may be done to prevent contamination of one fluid with another or the contamination of one fluid with the formation. A displacement fluid or as it is also known, a spacer fluid, may be water-based fluids. In most instances, spacer fluids may be used to separate drilling fluid from a cement composition during a cementing operation. Because the spacer fluid will be used to separate two other fluids, such as the drilling fluid and the cement composition, the spacer fluid should be compatible with both treatment fluids.
Switching between treatment fluids in a subterranean operation can be costly in both time and resources. Varied fluid types may require separate fluid storage, additional manpower, and additional equipment. In addition to the increased operating expenses, varied fluid use may create additional worksite problems such as higher environmental burdens, fluid incompatibilities, and the inability to reuse fluids and materials once their respective portion of the operation has been completed.